/**
 * Copyright (c) 2007-2008 Nearchos Paspallis
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/**
 * AspectSense
 *
 * Middleware for annotation-based, context-aware and adaptive services for
 * mobile and ubiquitous computing
 *
 * This project is an open-source effort, initiated by Nearchos Paspallis as
 * part of his PhD work at the University of Cyprus (http://www.ucy.ac.cy).
 *
 * More information about the project is available at "http://aspectsense.org".
 */

package org.aspectsense.annotations;

import org.aspectsense.evaluators.UtilityEvaluator;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.annotation.ElementType;

/**
 * This annotation must accompany each {@link Service} annotation, in order to
 * specify how the utility of the corresponding <i>service</i> is computed.
 *
 * @author Nearchos Paspallis [nearchos@cs.ucy.ac.cy]
 *         Date: Jan 2, 2008
 *         Time: 2:49:37 PM
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface ServiceUtility
{
    /**
     * Points to the actual service type targeted by this annotation.
     *
     * @return the type of the service targeted by this annotation
     */
    Class targetServiceType();

    /**
     * A simple tag allowing to add a description for the service utility. This
     * is a non-mandatory field as a default value is provided.
     *
     * @return a string-instance of the description
     */
    String description() default "Undescribed service utility specification";

    /**
     * Returns the class implementing the utility evaluator for this situation.
     *
     * @return an instance of {@link Class} extending the UtilityEvaluator
     */
    Class evaluatorType() default UtilityEvaluator.class;

    /**
     * Returns a set of pairs corresponding to constants to be used in the
     * utility function by the
     * {@link org.aspectsense.evaluators.UtilityEvaluator}. By default, this
     * returns an empty array.
     *
     * @return a set of pairs corresponding to constants to be used in the
     * utility function by the
     * {@link org.aspectsense.evaluators.UtilityEvaluator}. By default, this
     * returns an empty array.
     */
    String [] constants() default {};

    /**
     * Returns a string to be used for the formation of the utility function.
     * Eventually, this string is used by the
     * {@link org.aspectsense.evaluators.UtilityEvaluator}.
     *
     * @return a string expression of the utility function
     */
    String utilityFunction();
}